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The Reactive Chemisorption of Alkyl Iodides at Cu(110) and Ag(111) Surfaces: A Combined STM and XPS Study

Bushell, James, Carley, Albert Frederick, Coughlin, Mark, Davies, Philip Rosser, Edwards, Dyfan, Morgan, David John and Parsons, Martin 2005. The Reactive Chemisorption of Alkyl Iodides at Cu(110) and Ag(111) Surfaces: A Combined STM and XPS Study. Journal of Physical Chemistry B 109 (19) , pp. 9556-9566. 10.1021/jp0513465

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Abstract

The chemisorption of methyl and phenyl iodide has been studied at Cu(110) and Ag(111) surfaces at 290 K with STM and XPS. At both surfaces dissociative adsorption of both molecules leads to chemisorbed iodine, with the STM showing c(2 × 2) and ( × )R30 structures at the Cu(110) and Ag(111) surfaces, respectively. At the Cu(110) surface a comparison of coexisting c(2 × 2) I(a) and p(2 × 1) O(a) domains shows the iodine adatoms to be chemisorbed in hollow sites with evidence at low coverage for diffusion in the 11̄0direction. In the case of methyl iodide no carbon adsorption is observed at either the silver or the copper surfaces, but chemisorbed phenyl groups are imaged at the Cu(110) surface after exposure to phenyl iodide. The STM images show the phenyl groups as bright features approximately 0.7 nm in diameter and 0.11 nm above the iodine adlayer, reaching a maximum surface concentration after 6 Langmuir exposure. However, the phenyl coverage decreases with subsequent exposures to PhI and is negligible by 1000 L exposure, consistent with the formation and desorption of biphenyl. The adsorbed phenyls are located above hollow sites in the substrate, they are stabilized at the top and bottom of step edges and in paired chains (1.1 nm apart) on the terraces with a regular interphenyl spacing within the chains of 1.0 nm in the 11̄0 direction. The interphenyl ring spacing and diffusion of individual phenyls from within the chains shows that the chains do not consist of biphenyl species but may be a precursor to their formation. Although the XPS data shows carbon present at the Ag(111) surface after exposure to PhI, no features attributable to phenyl groups were observed by STM.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Cardiff Catalysis Institute (CCI)
Subjects: Q Science > QD Chemistry
Publisher: ASC Publications
ISSN: 1520-6106
Last Modified: 17 Jun 2017 01:54
URI: http://orca.cf.ac.uk/id/eprint/1413

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